Light field based projector calibration method and system

ABSTRACT

The present disclosure relates to a method for calibrating a projector. In one example, the method includes receiving by a processing element light field data corresponding to a calibration image projected by a projector and captured by a light field capturing device, and modeling by a processing element one or more intrinsic properties of the projector using the light field data and the calibration image. The calibration image may be projected by the projector directly into the light field capturing device.

TECHNICAL FIELD

The technology described herein relates generally to methods and systemsfor calibrating one or more projectors.

BACKGROUND

Image and/or video projectors may be used to project images onto aprojection surface, such as onto a screen, a wall, or other surface. Insome applications, projectors may be used to enhance, compliment, orotherwise augment objects on the projection surface to create a dynamicand enjoyable user experience, such as an amusement park attraction. Forexample, characters or objects may be projected on a surface to providean immersive environment for an amusement park goer.

Image and/or video projectors may include a number of limitations. Forinstance, some projectors may have limited color gamut and brightnessproperties. In addition, the image filtering hardware/software and/orthe lens configuration of some projectors may distort a projected imagesuch that differences exist between the projected image appearing on theprojection surface and the source image.

In these and other examples, the intrinsic calibration of projectors isoften required for high quality projection mapping applications. Themain goal of calibration is to estimate a model to accurately representthe optical system of the projector, including its field of view andoptical axis, among others, as well as the non-linear distortionoccurring due to its lens configuration.

Known calibration techniques, however, require significant userinteraction, are time-intensive, and are often not very accurate. Inaddition, current projector calibration methods are closely related tostandard camera calibration methods by treating the projector as aninverse of a camera and applying similar, adapted calibration methods tocompute the projector's parameters, which may not accurately model theintrinsic properties of the projector. As such, there exists a need fora technique that can be used to more accurately calibrate projectors.

SUMMARY

One example of the present disclosure relates to a method of calibratinga projector. The method includes receiving by a processing element lightfield data corresponding to a calibration image captured by a lightfield capturing device. The calibration image may be projected by aprojector directly into the light field capturing device. The methodalso includes modeling by a processing element one or more intrinsicproperties of the projector using the light field data and thecalibration image.

Another example of the present disclosure includes a system forcalibrating a projector. The system includes a projector configured toproject a calibration image, a light field capturing device configuredto capture at least a portion of the calibration image projected by theprojector, and a processing element in communication with the lightfield capturing device and configured to model one or more intrinsicproperties of the projector using light field data corresponding to thecalibration image captured by the light field capturing device. Thecalibration image may be projected by the projector directly into thelight field capturing device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a projection calibration system accordingto the present disclosure.

FIG. 2 is a simplified block diagram of the calibration system of FIG.1.

FIG. 3 illustrates an example calibration pattern or image for use incalibrating the projection system of FIG. 1.

FIG. 4 is a flow chart illustrating a method of calibrating a projectionsystem.

SPECIFICATION

The present disclosure is generally related to a system and method forcalibrating a projector. The projector projects a calibration image ortest pattern directly into a light field capturing device, such as ascanner that can sense directional light information (e.g., flatbedscanner with a directional light blocking layer), a light field camera,or other similar device capable of capturing the light fieldrepresentation of a scene. The light field capturing device converts thecaptured scene into light field data corresponding to the capturedcalibration image or test pattern. The system includes one or moreprocessing elements configured to receive the light field data. The oneor more processing elements model one or more intrinsic properties ofthe projector using the light field data and the calibration image. Forexample, based on the captured information, such as the intensity oflight from the projector as well as the direction that light rays aretraveling from the projector to the light field capturing device, theone or more processing elements can model the type and degree ofinternal distortions induced by the projector during the projectionprocess. More specifically, using the light field data and thecalibration image or test pattern, the one or more processing elementscan model the distortions to the projected image caused by theprojector's lens, the projector's image filtering systems, or the like.Using the modeled intrinsic properties of the projector, the system canaccount for and/or otherwise alleviate the distortions intrinsic to theprojector such that the image actually projected by the projector issubstantially similar to the image to be projected. In this manner, theprojector can be accurately modeled and input images can be modified tobe adjusted to project as desired.

FIG. 1 a schematic view of a calibration system 100. FIG. 2 is asimplified block diagram of the calibration system 100. Referring toFIGS. 1 and 2, the calibration system 100 may include a projector 102, alight field capturing device 104, and one or more processing elements106 (such as part of one or more computers or computer systems). The oneor more processing elements 106 may be in electrical communication withthe light field capturing device 104 either directly or indirectly(e.g., through a data transfer mechanism, wireless connection, or thelike). Depending on the particular application, the one or moreprocessing elements 106 may also be in electrical communication with theprojector 102. The electrical communication(s) may permit the variouselements of the calibration system 100 to share and transportinformation (e.g., data) between the various elements. For example, theone or more processing elements 106 may receive data (such as lightfield data, light ray date, or intrinsic properties of the light fieldcapturing device 104, among others, as explained below) from the lightfield capturing device 104 via the electrical communication between theone or more processing elements 106 and the light field capturing device104. The one or more processing elements 106 may also transmit dataand/or instructions (e.g., commands) to the light field capturing device104 via the electrical communication between the one or more processingelements 106 and the light field capturing device 104, such as to causethe light field capturing device 104 to begin operation, among others.

Additionally or alternatively, the one or more processing elements 106may receive data from the projector 102 (such as default parameters ofthe projector 102, the status of the projector 102, etc.) via theelectrical communication between the one or more processing elements 106and the projector 102. The one or more processing elements 106 may alsotransmit data and/or instructions (e.g., commands) to the projector 102via the electrical communication between the one or more processingelements 106 and the projector 102, such as to modify the projectioncharacteristics of the projector 102, as explained below.

The projector 102 may be substantially any type of device operable toemit light into different directions, such as to project an image (suchas a still image and/or video images). For example, the projector 102may be a conventional projector, a laser projector, a cathode ray tubeprojector, a micro-electro-mechanical projector, a digital lightprocessing projector, a liquid crystal display projector, or a liquidcrystal on silicon projector, among others. The projector 102 may be anytype of light and may be a lens-based or non-lens based device (e.g.,may include one or more mirrors or reflectors). For example, in someembodiments, the projector 102 may project red, green, and/or blue lightwavelengths. In some embodiments, the projector 102 may projectsubstantially any other color or frequency of light, including visibleand/or invisible light (e.g., ultraviolet, infrared, and others), asnecessary. It should be noted that the sensing device should correspondto and be able to detect the type of light being projected. In thismanner, the calibration methods and systems discussed herein may be usedwith substantially any type of projector, and as such, the discussion ofany particular embodiment is meant as illustrative only.

In connection with calibrating the projector 102, the projector 102 maybe configured to project a test pattern or calibration image 120. Asexplained below, the calibration image 120 is used to determine theintrinsic properties and/or distortions of the projector 102. Forexample, by comparing the calibration image 120 with the image and/orlight field actually projected by the projector 102, the calibrationsystem 100 can determine the type and degree of internal distortionsinduced by the projector 102 during the projection process, such asdistortions to the projected image caused by the lens distortion,optical axis of the projector, focal length, image filtering hardwareand/or software, or the like. As a specific example, the calibration candetermine the focal length of the projector, such as the way the lightspreads outwards from the projector. Other examples include estimatingwavelength dependent distortions, point spread function, or the like.These intrinsic properties or distortions of the projector 102 can thenbe accounted for in the projection system, such as by applyingadditional modifications or filters to a source image and/or videosignal to cancel out any intrinsic distortions, as provided more fullybelow.

In some embodiments, the projector 102 may project the calibration image120 onto a projection surface 122 (see FIG. 1), though such a step isnot essential to calibrating the projector 102. Such a step, however,may be beneficial to provide visual indication to the user thatdistortions exist in the projected image and after calibration, theprojector 102 will project the corrected images onto the projectionsurface 122. The projection surface 122 may be substantially any type ofopaque surface or object. For example, the projection surface 122 may beflat, non-planar, or varying, and may include one or more textures,surface variations, or colors. In some instances, the projection surface122 may include multiple surfaces positioned relative to one another.The type and structure of the projection surface 122 may be varied asdesired.

The light field capturing device 104 will now be discussed in moredetail. The light field capturing device 104 is any device capable ofcapturing the light field (and/or any other light emitting properties)of the projector 102. For example, the light field capturing device 104may be any device capable of acquiring an accurate light fieldrepresentation of the observed scene. In some embodiments, the lightfield capturing device 104 may be a light field camera or an imagesensor with a light field filter, such as a scanner, among others. Thelight field capturing device 104 may be used on its own or with one ormore filters, screens, or layers that can provide or allow determinationof directional data. For example, a screen or filter may be placed infront of the light field capturing device 104, such as on a flatbedscanner. In such embodiments, the screen or filter allows the lightfield capturing device 104 to acquire the direction of the light emittedfrom the projector 102. For example, the screen or filter may include aplurality of holes defined therethrough, the holes sized and positionedsuch that the gathered light includes a measurable directionalcomponent. In many embodiments, the light field device should be able tosufficiently estimate (or capture data enabling such estimations) theray directions for different positions for at least a part of the imageplane of the projector.

As described herein, the light field capturing device 104 is configuredto capture at least a portion of the calibration image 120 projected bythe projector 102. For example, the light field capturing device 104 mayinclude an optical system, such as one or more lenses 124. In someembodiments, the light field capturing device 104 may not include a lensand rather may include lens alternatives such as, but not limited to,shaped mirrors and/or reflectors. The lens 124 of the light fieldcapturing device 104 may be a conventional lens or any othertransmissive optical device operable to gather and/or focus light intothe light field capturing device 104. In this manner, the light fieldcapturing device 104 captures information about the light fieldemanating from the projector 102, such as the intensity of light fromthe projector 102 as well as the direction that light rays 126 aretraveling. For example, the light field capturing device 104 may capturethe individual spatially varying light rays 126 such that theirdirections can be estimated by the acquired light field. The light fieldinformation captured by the light field capturing device 104 may beconverted to light field data and transmitted to the one or moreprocessing elements 106 for analysis and/or storage.

As shown in FIG. 1, the light field capturing device 104 may bepositioned relative to the projector 102 (e.g., relative to a projectinglens 130 of the projector 102). For example, the light field capturingdevice 104 may be spaced from the projecting lens 130 a distance D.Depending on the particular application, the distance D may be apredefined distance or may vary during specific implementation of thecalibration system 100. It should be noted that the distance D dependson the setup, the type of projector, light field capturing device, anddesired sensitivity for the calibration.

As one example, when using a scanner with a blocking layer havingapertures defined therethrough, the distance D should be selected toensure that the individual rays are captured by singular apertures suchthat there is not substantial overlap between the apertures. As oneparticular example that may be used to capture the entire image plane, aflatbed scanner having a blocking layer was used with a mobileprojector. In this example, the projector was about 1.5 feet from thescanner and the mask layer or blocking layer was about 0.5 feet from thescanner. However, this distance depends on many factors and may bemodified as desired.

The light field capturing device 104 may capture at least a portion(e.g., less than 50%, about 50%, greater than 50%, etc.) of thecalibration image 120 for further processing by the one or moreprocessing elements 106. That said, often times, the light fieldcapturing device 104 will capture the entire or substantial portion ofthe light rays 126 comprising the calibration image 120. For instance,the calibration image 120 may be captured by the light field capturingdevice 104 from at least one angle such that the whole image plane ofthe projector 102 is at least sparsely acquired. In some embodiments,only a portion of the image plane of the projector 102 may be acquired.In such embodiments, the calibration system 100 may be configured toestimate the distortions across the entire image plane based on thesparsely acquired data. For instance, distortions occurring at the edgesof the projected image may be assumed to exist along each edge of theprojected image. Other captured distortions may also be assumed to existsymmetrically across the image plane of the projector 102. In someembodiments, the calibration system 100 may be configured to account forasymmetrical distortions across the image plane. Alternatively oradditionally, the light field capturing device may be used to capturemultiple images, where each of the images captures a different sectionof the image plane, such that all images can be analyzed to assess theentire image plane. Or in instances where only a portion of the imageplane is of interested, the light field camera may capture only thatportion. As shown in FIG. 1, the calibration image 120 may be projectedby the projector 102 directly into the lens 124 of the light fieldcapturing device 104, though other suitable configurations arecontemplated.

Any number of light field capturing devices 104 may be used. For thesake of simplicity, however, only one light field capturing device 104is shown in FIG. 1. In embodiments with two or more light fieldcapturing devices 104, the light field capturing devices 104 may bespaced from one another (either at a set distance or at a varyingdistance). In some embodiments, multiple light field capturing devices104 may be positioned immediately adjacent one another. In suchembodiments, the data captured by the two or more light field capturingdevices 104 may be analyzed together by the one or more processingelements 106. Depending on the particular application, the use of two ormore light field capturing devices 104 may provide greater accuracy inmodeling the intrinsic properties and/or distortions of the projector102.

With continued reference to FIGS. 1 and 2, the calibration system 100includes one or more processing elements 106, which may be referred tosimply as processors. As noted above, the one or more processingelements 106 analyze data received from the light field capturing device104 and/or the projector 102. In some embodiments, the one or moreprocessing elements 106 may optionally control one or more functions ofthe light field capturing device 104 and/or the projector 102. The oneor more processing elements 106 may be associated with a computingdevice 140, such as a computer, a server, a tablet, a smartphone, or anyother device capable of processing data. In some embodiments, the one ormore processing elements 106 may be part of a computing system definedintegrally with the projector 102 or the light field capturing device104. In other embodiments, the one or more processing elements 106 maybe part of a computing system separate from both the projector 102 andthe light field capturing device 104 (see FIG. 1).

In the examples of FIGS. 1 and 2, only one computing device 140 isshown; however, any number of computing devices 140 may be used. For thesake of convenience only, the description below will refer to a singlecomputing device 140. Similarly, the description below will refer to asingle processing element 106, though any number of processing elements106 (which may or may not be in direct communication) is contemplated.Where appropriate, the description of the computing device 140 below canbe applied to each computing device 140 of the calibration system 100.Similarly, the description of the processing element 106 below can beapplied to each processing element 106 of the calibration system 100,where applicable. Thus, reference to “the processing element” may referto the same processing element 106 or to a different processing element106 within the calibration system 100.

Referring to FIG. 2, the computing device 140 may include the one ormore processing elements 106, one or more memory components 142, a powersource 144, a display 146, and an input/output (I/O) interface 148. Thecomputing device 140 may also include other components typically foundin computing systems, such as communication interfaces and one or moresensors, among others. Each element of the computing device 140 may bein communication via one or more system buses 150, wirelessly or thelike. Each element of the computing device 140 will be discussed in turnbelow.

The processing element 106 may be substantially any type of electronicdevice capable of processing, receiving, and/or transmittinginstructions. For example, the processing element 106 may be amicroprocessor or a microcontroller. Additionally, it should be notedthat select components of the computing device 140 may be controlled bya first processing element 106 and other components may be controlled bya second processing element 106, where the first and second processingelements 106 may or may not be in communication with each other.Additionally or alternatively, select calibration steps may be performedby one processing element 106 with other calibration steps performed bydifferent processing elements 106, where the different processingelements 106 may or may not be in communication with each other.

The one or more memory components 142 store electronic data that is usedby the computing device 140 to store instructions for the processingelement 106, as well as to store presentation and/or calibration datafor the calibration system 100. For example, the one or more memorycomponents 142 may store data or content, such as, but not limited to,audio files, video files, and so on, corresponding to variousapplications. The one or more memory components 142 may bemagneto-optical storage, read only memory, random access memory,erasable programmable memory, flash memory, or a combination of one ormore types of memory components.

The power source 144 provides power to the components of the computingdevice 140. Depending on the particular application, the power source144 may be a battery, a power cord, or any other element configured totransmit electrical power to the components of the computing device 140.

The display 146 provides visual feedback to a user. In some embodiments,the display 146 can act as an input element (e.g., a touch screendisplay) to enable a user to control, manipulate, and calibrate variouscomponents of the calibration system 100. The display 146 may be anysuitable display, such as a liquid crystal display, a plasma display, anorganic light emitting diode display, and/or a cathode ray tube display.In embodiments where the display 146 is used an input, the display 146may include one or more touch or input sensors, such as one or morecapacitive touch sensors, a resistive grid, or the like.

The I/O interface 148 provides communication to and from the computingdevice 140, such as to or from the light field capturing device 104, theprojector 102, or any other device (e.g., other computing devices,auxiliary scene lighting, auxiliary sensors, speakers, etc.). The I/Ointerface 148 may include one or more input buttons, a communicationinterface (such as WiFi, Ethernet, Bluetooth, or the like),communication components (such as universal serial bus (USB)ports/cables), or the like.

FIG. 3 illustrates an example calibration pattern or image for use incalibrating the projection system. As part of the calibration process,the projector 102 projects the calibration image 120 directly into thelight field capturing device 104, such as directly into the lens 124 ofthe light field capturing device 104. In particular, the light fieldcapturing device 104 captures the projected light directly from theprojector 102, as opposed to capturing reflected light off of anintermediate surface, such as off of the projection surface 122. In thismanner, the light field capturing device 104 may capture the lightemitted from the projector 102 without interfering elements or surfaces.For example, the light field capturing device 104 may capture thephotons of light emitted by the projector 102 without the photons beingreflected or otherwise modified. As such, the light field capturingdevice 104 may capture the calibration image 120 projected by theprojector 102 without the need of a projection surface altogether. Ininstances where the light field capturing device includes a blockinglayer, the light that reaches the light field capturing device is notdistorted, but the percentage of light reaching the device may bereduced to a fraction of the overall light.

The calibration image 120 may be a predefined, structural lightarrangement having one or more pattern elements 160. For example, thecalibration image 120 may include one or more regions with substantiallyconstant properties, or properties that are varied, within a prescribedrange of values. The pattern elements 160 may be similar to, ordissimilar from, each other in at least one characteristic. Thecalibration image 120 may be constructed in such a way that the locationof each pattern element 160 may provide identifying information. Forinstance, each pattern element 160 may include an identifier associatetherewith that can be explicitly displayed and/or implicitly deduced.

As shown in FIG. 3, the pattern elements 160 may be an array of dots orother shapes. Depending on the particular embodiment, the patternelements 160 may be in the shape of a circle, a plus sign, a square, orother suitable geometric shape. The pattern elements 160 may alsoinclude localized or structured changes in variations in color, hue,intensity, polarization, or tint, where these characteristics mayprovide additional data points to be tracked or may form the patternelements 160 themselves. The pattern elements 160 may be arranged inrows and columns, either symmetrically or asymmetrically. Additionallyor alternatively, the pattern elements 160 may be distributed in astructured uniform or non-uniform manner. For example, as shown in FIG.3, the pattern elements 160 may be arranged such that each patternelement 160 is positioned equidistant to adjacent pattern elements 160.The number of pattern elements 160 may be varied based on the desiredaccuracy for the calibration. For example, increasing the number ofpattern elements 160 may increase the sensitivity and/or accuracy of thecalibration, and vice versa. FIG. 3 illustrates one exemplaryembodiment, and any other pattern with different arrangementcharacteristics or features may be used. As such, the discussion of anyparticular embodiment is meant to be illustrative only.

FIG. 4 is a flow chart illustrating a method 200 for calibrating aprojection system, such as the projector 102. Referring to FIG. 4, themethod 200 may begin with determining the intrinsic properties of thelight field capturing device 104 (Block 202). Determining the intrinsicproperties of the light field capturing device 104 may include acquiringthe properties either through vendor information (via web or printmedia), directly from the light field capturing device 104 itself, orthrough calibration methods (such as well-known light field cameracalibration methods). For example, the intrinsic properties of the lightfield capturing device 104 may be provided by the manufacturer andstored directly on the light field capturing device 104. In suchembodiments, the intrinsic properties of the light field capturingdevice 104 may be acquired by the computing device 140 once electricalcommunication is made between the computing device 140 and the lightfield capturing device 104. In other embodiments, the user may enter theintrinsic properties of the light field capturing device 104 into thecomputing device 140 after acquiring such information in available webor print media (e.g., online or print owner's manuals, etc.). The usermay also enter generally acceptable properties that may cover a widerange of light field capturing devices. The intrinsic properties of thelight field capturing device 104 may be stored on the computing device140 (e.g., on the one or more memory components 142 and/or on the one ormore processing elements 106, etc.) for use in calibrating the projector102, as detailed below.

In some embodiments, the method 200 may include projecting a testpattern, such as the calibration image 120, by the projector 102 (Block204). As noted above, the projector 102 may be operable to project thecalibration image 120 directly into the lens 124 of the light fieldcapturing device 104. For instance, as explained above, the projector102 may emit photons of light unobstructedly into the lens 124 of thelight field capturing device 104 (i.e., without an intermediate surfacepositioned therebetween). More particularly, a straight light path mayextend from the projector 102 to the lens 124 of the light fieldcapturing device 104 absent an intermediate image formation, such as ona surface.

In any case, the method 200 may include capturing the calibration image120 by the light field capturing device 104 (Block 206). In suchembodiments, the light field capturing device 104 captures the projectedlight making up the captured calibration image 120 into light field datacorresponding to the calibration image 120. The light field data mayinclude the intensity of light from the projector 102 as well as thedirection that the light rays 126 are traveling from the projector 102to the light field capturing device 104.

With continued reference to FIG. 4, the method 200 includes receiving bythe processing element 106 the light field data corresponding to thecalibration image 120 captured by the light field capturing device 104(Block 208). As noted above, the light field data may be communicated tothe processing element 106 via electrical communication between thelight field capturing device 104 and the computing device 140. Dependingon the particular application, the computing device 140 may be hardwiredto the light field capturing device 104. In some embodiments, thecomputing device 140 may be selectively connected to the light fieldcapturing device 104, such as via a communication cable (e.g., a USBcable, a mini USB cable, or the like), via a communication device (e.g.,memory chip), and/or via wireless communication protocols (e.g., WiFi,Bluetooth, etc.).

As shown in FIG. 4, the method 200 may include estimating by theprocessing element 106 a position of the light field capturing device104 relative to the projector 102 using the calibration image 120 (Block210). For example, based on the light field data received from the lightfield capturing device 104 as well as the intrinsic properties of thelight field capturing device 104, the processing element 106 mayestimate the distance D of the light field capturing device 104 from theprojector 102. For example, a lower angle of incidence of the light raydirections captured by the light field capturing device 104 may indicatea smaller distance D. In like manner, a higher angle of incidence of thelight ray directions captured by the light field capturing device 104may indicate a larger distance D. In like manner, differing angles ofincidence associated with opposing sides of the captured calibrationimage 120 may indicate that the light field capturing device 104 ispositioned at a nonparallel angle to the image plane of the projector102.

In some embodiments, the method 200 may include estimating, by theprocessing element 106, directions of light rays 126 emitted by theprojector 102 when projecting the calibration image 120 by utilizinglight ray data (Block 212). For example, using the position of the lightfield capturing device 104 estimated in Block 210, the processingelement 106 can analyze the light ray angles of incidence to estimatethe directions of the light rays 126 being emitted by the projector 102in projecting the calibration image 120. In this manner, the processingelement 106 can estimate or model what the projected image will looklike on a projection surface, such as on the projected surface 122.Depending on the particular application, the method 200 may includetransforming by the processing element 106 the captured information fromray representations to a simplified model (Block 214). For example, theprocessing element 106 may transform the captured information from rayrepresentations to a pinhole model, though other suitable simplifiedmodels are contemplated.

With continued reference to FIG. 4, the method 200 includes modeling bythe processing element 106 one or more intrinsic properties of theprojector 102 using the light field data and the calibration image 120(Block 216). In one embodiment, the processing element 106 may analyzethe light field data to detect the location of the pattern elements 160using an image analysis algorithm that can detect the locations of thepattern elements 160. As some examples, image processor operators, suchas blob detection and center of gravity estimation, line detection,structured light processing using binary gray codes, or the like can beused. In short, substantially any method that generates mapping from thelight field capturing device image plane to the image plane of theprojector can be used. When the light field capturing device is a lightfield camera, this analysis can provide the ray direction informationdirectly. When the light field capturing device is a scanner with ablocking layer, the directionality of the light may be estimated duringthe calibration process.

Using the image analysis above, the processing element 106 may reviewthe captured projected image against the calibration image 120 to detectregions that differ in one or more properties, such as, but not limitedto, brightness, color, hue, and position. For example, depending on theintrinsic properties and/or distortions of the projector 102, thepattern elements 160 captured by the light field capturing device 104may have a different color, brightness, and/or position compared to thecalibration image 120. Once the captured pattern elements 160 have beendetected and compared against the calibration image 120, the processingelement 106 may model the intrinsic properties of the projector 102. Forexample, using the light field data and the calibration image 120, theprocessing element 106 can model the distortions to the projected imagecaused by the projector's lens, the projector's image filtering systems,or the like.

Continuing to refer to FIG. 4, the method 200 may include modifying bythe processing element 106 a source image to be projected by theprojector 102 based on the modeled intrinsic properties of the projector102 (Block 218). For example, based on the modeled intrinsicproperties/distortions of the projector 102, the processing element 106may modify or otherwise alter an input signal to the projector 102 suchthat the image actually projected substantially matches the image to beprojected. For example, and without limitation, the processing element106 may modify the input signal to brighten areas that are otherwisedarkened to the intrinsic properties of the projector 102. In likemanner, the processing element 106 may modify the input signal to moveportions of a projected image that would otherwise be skewed due to theintrinsic properties of the projector 102.

The method 200 disclosed herein may be used in various situations. Forexample, the intrinsic properties and/or distortions of the projector102 may be canceled out or otherwise accounted for such that the imageactually projected by the projector 102 appears as close to the image tobe projected. In other examples, a first type, model, or serial numberof projector may include a first set of intrinsic properties and/ordistortions affecting the projected image in a first manner. A secondtype, model, or serial number of projector may include a second set ofintrinsic properties and/or distortions affecting the projected image ina second manner. In such examples, the method 200 disclosed herein canmodel (and account) for the varying intrinsic properties/distortionsand/or wavelength dependent issues between the two projectors such thatthe images actually projected by the first and second projectors appearsubstantially similar.

The above specifications, examples, and data provide a completedescription of the structure and use of exemplary embodiments of theinvention as defined in the claims. Although various embodiments of thedisclosure have been described above with a certain degree ofparticularity, or with reference to one or more individual embodiments,those skilled in the art could make numerous alterations to thedisclosed embodiments without departing from the spirit or scope of theclaimed invention. Other embodiments are therefore contemplated. It isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as only illustrative ofparticular embodiments and not limiting. Changes in detail or structuremay be made without departing from the basic elements of the inventionas defined in the following claims.

What is claimed is:
 1. A method of calibrating a projector, the method comprising: receiving by a processing element light field data corresponding to a calibration image captured by a light field capturing device, wherein the calibration image is projected by a projector directly into a light field capturing device; estimating by the processing element directions of light rays emitted by the projector when projecting the calibration image by utilizing light ray data; and modeling by a processing element one or more intrinsic properties of the projector using the light field data and the calibration image.
 2. The method of claim 1, further comprising estimating by the processing element a position of the light field capturing device relative to the projector using the calibration image.
 3. The method of claim 1, further comprising transforming by the processing element the captured information from ray representations to a simplified model.
 4. The method of claim 3, wherein the captured information is transformed from ray representations to a pinhole model.
 5. The method of claim 3, further comprising modifying by a processing element a source image to be projected by the projector based on the modeled intrinsic properties of the projector.
 6. The method of claim 1, wherein the calibration image is captured by the light field capturing device from at least one angle such that the whole image plane of the projector is at least sparsely acquired.
 7. The method of claim 1, wherein the calibration image is projected by the projector onto a projection surface.
 8. The method of claim 1, further comprising determining the intrinsic properties of the light field capturing device.
 9. A system for calibrating a projector, the system comprising: a projector configured to project a calibration image; a light field capturing device configured to capture at least a portion of the calibration image projected by the projector, wherein light rays making up the calibration image are projected into the light field capturing device without reflecting on an intermediate surface; and a processing element in communication with the light field capturing device, wherein the processing element is configured to: estimate directions of light rays emitted by the projector when projecting the calibration image by utilizing ray data; transform the ray representations to a simplified model; and model one or more intrinsic properties of the projector using light field data corresponding to the calibration image captured by the light field capturing device.
 10. The system of claim 9, wherein the processing element is further configured to estimate a position of the light field capturing device relative to the projector using the light field data captured by the light field capturing device.
 11. The system of claim 10, wherein the simplified model is a pinhole model.
 12. The system of claim 9, wherein the processing element is part of a computing system separate from the projector and the light field capturing device.
 13. The system of claim 9, wherein the processing element is part of a computing system defined as part of the projector or the light field capturing device.
 14. The system of claim 9, wherein the light field capturing device is a light field camera or a scanner.
 15. The system of claim 2, wherein estimating by the processing element directions of light rays emitted by the projector comprises: analyzing angles of incidence of the light rays at the capturing device and the position of the light field capturing device relative to the projector to estimate the directions of the light rays.
 16. The system of claim 10, wherein the position of the light field capturing device and incident angles of light rays at the light field capturing device are used to estimate the directions of the light rays emitted by the projector when projecting the calibration image. 